This invention relates to an improved continuous grain flow, concurrent-countercurrent type grain dryer.
Grain, particularly corn, is often dried after picking and before storage to prevent wet pockets, mildew and consequent spoilage. Fast, efficient drying may be effected by the introduction of a generally heated, low moisture content drying medium (usually air) to the wet grain. The drying medium is moved relative to the grain and accumulates moisture from the grain. The moist saturated drying medium is then removed from contact with the grain with the result that the grain has a relatively lower moisture content.
Various types of grain dryers have been disclosed by the prior art. For example, Meiners et al in U.S. Pat. No. 3,727,323 discloses a concurrent-countercurrent grain dryer including a preheater means. Grain is introduced to the top of a bin and removed from the bottom in a continuous process. Cold air is introduced through cold air inlets adjacent the bottom of the bin for countercurrent flow. Hot dry air is introduced adjacent the top of the bin for concurrent flow. Both flows are removed at an intermediate position within the bin through exhaust ducts. An additional set of preheater ducts which serve an exhaust function are positioned above the hot air inlet ducts.
While such a grain drying mechanism provides adequate results, additional research and experimentation has shown that the exhaust air discharged from the grain dryer is often not fully moisture laden, nor is the temperature adequately reduced to achieve maximum efficiency by the dryer. To improve the efficiency of moisture and heat transfer between the drying medium (air) and the material being dried (grain), is a desirable objective in a grain drying system. Maintenance of the concurrent-counter current method of drying the grain is also desirable in order to maximize grain condition.